Originally Posted by match55
lighting is the one came with the tank...
That's not telling us much! You might want to put in your "My Tanks" what your actual lighting is - type, length, and wattage.
Coralline doesn't need much light. In fact, it will bleach white with too much light. Eventually, you'll end up with coralline everywhere. It does need *some* light, but don't expect the undersides of your rocks to be white. As long as your calcium/alkalinity levels stay good (and yours look good), it should grow given time.
From time to time, I have sections of my coralline go white on me - I've never figured out why though. It always comes back though. It's just one of those things...